Duplicate exstrophy of the bladder.

Duplicate exstrophy is a very rare variant of the exstrophy complex. Treatment is gratifying, because the patients have normal internal urogenital structures. Two different cases of duplicate exstrophy are presented. One is completely similar to the type, described by Marshall and Muecke, of which now 9 cases have been reported. It is suggested that the other, together with 4 earlier reported cases, belongs to a different type of duplicate exstrophy. The embryological mechanism responsible for this type is probably a coincidence of 1) duplication of cloacal structures and 2) exstrophy of one of the bladders.